Setup for the practice course is pretty good for the main courses.  Depends on the elements of the practice course, but usually the practice course is excellent for getting ready for the Pro, at least.  Nationals courses are longer and faster, so you may need to adjust tracks.  But I’m a hack so ask around in Lincoln.

I have always felt that you can get a decent base setup at the practice course, but depending on what day of the week it is the amount of OPR and rubber on the practice course can be very different. Also since the practice course is normally the same every year the concrete is worn were the line is and has a slightly different grip level over the main courses.
Keep in mind that Thursday and Friday the temperatures are foretasted to be in the mid to upper 70s so tire temps and surface temps may be a factor.